What are my options as to wildcats that will fit in an AR magazine and can be made from 5.56 brass?

I know there is the .30 whisper, but there must be others, just curious. I'm aware the .30 Whisper is not "based" on the .223/5.56 case, but it can be made from a .223/5.56 case. Basically, I'm trying to find another use for all this brass, I've got.

Isn't there a cartridge where you neck the .223 case all the way up to .338 removing the bottleneck completely?

Thangs,
Bean

Paid Advertisement

--

thomas41 [Member]

5/19/2010 5:50:06 AM EDT

I have see the 6/45. It is a .223 necked up to 6mm. With correct twist can us 85 to 90 gr bullet. Don't know if this is of and interest to you.

LLCoolBeans [Team Member]

5/19/2010 5:55:11 AM EDT

Originally Posted By thomas41:I have see the 6/45. It is a .223 necked up to 6mm. With correct twist can us 85 to 90 gr bullet. Don't know if this is of and interest to you.

Sure it's of interest. I want to learn about them all. Thanks.

kallnojoy [Team Member]

5/19/2010 5:57:50 AM EDT

7.62x40 Kurt

good thread on it in the variants forum.

It's one I've got my eye on if he does another batch of dies and barrels.

The 7.62x40mm is a .223 based wild-cat offering for the service rifle family of weapons and was created by Kurt Buchert of Lake Charles, Louisiana.

First thoughts began in September of 2005 as the result of many sleepless Hurricane Rita nights huddled around lanterns thinking and talking about the use of the 300-221 as a medium-sized game hunting cartridge in a service rifle platform. The thought or goal was to wild-cat an improved .30 caliber cartridge that would take advantage of as much of the .223 parent case capacity with a 125 grain bullet and still load and function in standard service rifle magazines and mechanism components. The selection of the .30 caliber projectile in this weight class was based on the calculated velocity window of 2,400 to 2,500 fps and decades of industry wide reloading, hunting, and military experience. The compiled information showed that the 110 to 125 grain projectiles performed well at these intermediate velocities while delivering modest recoil and a high degree of controllability and accuracy in manual and gas operated weapons.

Following the intermediate cartridge concept of the 7.92x33mm kurz, 7.62x39mm Russian, 7.92x40mm CETME, and 7.62x40mm CETME from the 40’s and 50’s the 7.62x40mm is a culmination of firearms industry, wild-cat, benchrest, and personal experience and information. The chamber dimensions went through several revisions in an effort to produce the best all-around compromise of feeding, case capacity, velocity, accuracy, and chamber release. The intersection of these efforts has come to what individual owners and industry leaders spoken with have called a “makes-sense” cartridge for intermediate power in a service rifle platform.

The 7.62x40mm is derived from the 5.56x45mm (.223 Rem.) parent case. The low cost and availability of mil-surplus and commercial brass was one of the core reasons for the development of this cartridge.

Primarily designed to use 7.62mm (.308) projectiles in the 110 to 125gr range, but has been loaded and tested up to 220gr in sub-sonic applications. The range of bullet weights and designs in the .308 family make this a very flexible cartridge.

The user selectable ballistic performance makes it an excellent choice for varmint control, medium sized game hunting, or personal defense. As illustrated below in a comparison of the .223 and 7.62x40mm.

.223 load of a 55gr FMJBT at 3,000 fps will produce an average of:
1,100 ftlbs of energy at the muzzle
885 at 100 yards
710 at 200 yards
565 at 300 yards with a 5.4” high flight path

7.62x40mm load of a 125gr BTBT at 2,500 fps will produce an average of:
1,730 ftlbs of energy at the muzzle
1,430 at 100 yards
1,175 at 200 yards
960 at 300 yards with a 7.6” high flight path

The 7.62x40mm makes the most of standard rifle components, usually only requiring a barrel change while still offering the end user the ability to customize the rifle with their choice of buffer and gas systems. You can still tune the rifle for timing and felt recoil which makes the whole system more user friendly and reduces wear and tear on the rifle, does not require any proprietary parts to function.

For current 300-221 / 300 Whisper users it is a natural progression if looking for more velocity. Simply have the barrel re-chambered, cut and form new brass, adjust your reloading dies for the longer round, reload and head to the range.

The information in this document is not inclusive of all that has gone into the 7.62x40mm cartridge, the thousands of rounds reloaded and fired, experiments with magazines, chamber revisions and results, or the performance of barrel and gas system length…..

This is meant to serve as core information, a conversation starter, and a holding area for those who wish to share their experience with the 40...

line-up of 300-221, 7.62x39mmRussian, 7.62x40mm, and 5.56x45mm

Aggie_Gunner [Team Member]

5/19/2010 6:55:01 AM EDT

The 6x45mm is an excellent cartridge, and IMHO is the easiest wildcat to convert an AR15 into...

- Same bolt
- same mags
- same barrel extension
- Same brass

Just need to get a blank in .243, chamber it (several companies make the reamers) and correctly drill the gas port.

THere is a local smith here, Ed Vandenberg, who does a great job with these.

The 300 whisper can easily use 556/223 brass for forming (I am using the CH4D forming die) and I would believe that the other whisper cases could use 556/223 brass as well since the case dimensions are so similar to the 221 fireball. The only problem is that some makes of brass may require the necks to be turned down because they are too thick (LC brass does not have this issue) with the 300 whisper and the issue would be magnified using even smaller neck dimensions like the 6.5 & 7mm.

What is your goal with this cartridge: subsonic, long range, plinking, inexpensive, varmits, hunting? The answer to that may help narrow your choices and get you some better recommendations.

JamesP81 [Team Member]

5/19/2010 9:09:54 AM EDT

Originally Posted By LLCoolBeans:
What are my options as to wildcats that will fit in an AR magazine and can be made from 5.56 brass?

I know there is the .30 whisper, but there must be others, just curious. I'm aware the .30 Whisper is not "based" on the .223/5.56 case, but it can be made from a .223/5.56 case. Basically, I'm trying to find another use for all this brass, I've got.

Isn't there a cartridge where you neck the .223 case all the way up to .338 removing the bottleneck completely?

Thangs,
Bean

6 x 45 is 223 necked up 6mm/.243. Ballistics numbers on it look good.

Though it's not a traditional AR caliber, some silhouette shooters use 7mm TCU, which is 223 necked up to 7mm/.284. I don't know if it would fit an AR magazine or not. If it did and could get a custom barrel made for it, I guess it'd work.

LLCoolBeans [Team Member]

5/19/2010 12:24:26 PM EDT

I'm liking the 7.62x40 Kurt. Looks like it's going through some political difficulties at the moment. That's lame. Looks like the ideal thing though, stuff a standard run of the mill 147gr .308 bullet into a 5.56 case. Simple, brilliant. I hate it when politics gets in the way of good ideas.

I was pretty sure there was a wildcat where the .223 case was necked wide open and a .338 bullet was stuffed in there. I'm sure that's been done.

Maybe I need to spec my own. Could call it the .338 Bean.

Scalce [Member]

5/19/2010 12:44:53 PM EDT

Originally Posted By LLCoolBeans:I'm liking the 7.62x40 Kurt. Looks like it's going through some political difficulties at the moment. That's lame. Looks like the ideal thing though, stuff a standard run of the mill 147gr .308 bullet into a 5.56 case. Simple, brilliant. I hate it when politics gets in the way of good ideas.

I was pretty sure there was a wildcat where the .223 case was necked wide open and a .338 bullet was stuffed in there. I'm sure that's been done.

The name doesn't ring a bell, but that appears to be a 5.56 case necked up to .338. Cool. I wrote BWE, let's see what they have to say.

Scalce [Member]

5/19/2010 12:54:11 PM EDT

Originally Posted By LLCoolBeans:

338 Thumper?

The name doesn't ring a bell, but that appears to be a 5.56 case necked up to .338. Cool. I wrote BWE, let's see what they have to say.

From BWE Firearms:

We are just getting the info on the 338 THUMPER put together. As I get more information I will post it here. The 338 uses a 223 case cut back to the start of the shoulder and you stick a 338 bullet in it. It uses standard 223 mags and bolts. We will be carrying dies for the 338. We will be selling uppers and not full guns. We are not sure at this point if we will sell just barrels or not.

LLCoolBeans [Team Member]

5/19/2010 1:09:44 PM EDT

Good enough. So long as I don't have to cut the chamber or calculate the size of the gas hole on myself, I'd be willing to purchase the entire upper. It's just more spare parts. Of course I'd rather just buy the barrel, but I suppose they hold the cards.

Great idea, just trim till the shoulder is gone and stuff a .338. Sweet.

Any ballistic data around?

Scalce [Member]

5/19/2010 1:16:42 PM EDT

Originally Posted By LLCoolBeans:Good enough. So long as I don't have to cut the chamber or calculate the size of the gas hole on myself, I'd be willing to purchase the entire upper. It's just more spare parts. Of course I'd rather just buy the barrel, but I suppose they hold the cards.

Great idea, just trim till the shoulder is gone and stuff a .338. Sweet.

Any ballistic data around?

It's so new that there is very little info.

Pretty much what is on their site and on Quarterbore.

225 gr.-300gr. will be subsonic and we are hoping to push the 160 gr. to about 2000 fps.

imtheflash [Team Member]

5/19/2010 1:27:14 PM EDT

Originally Posted By JamesP81:

Originally Posted By LLCoolBeans:
What are my options as to wildcats that will fit in an AR magazine and can be made from 5.56 brass?

I know there is the .30 whisper, but there must be others, just curious. I'm aware the .30 Whisper is not "based" on the .223/5.56 case, but it can be made from a .223/5.56 case. Basically, I'm trying to find another use for all this brass, I've got.

Isn't there a cartridge where you neck the .223 case all the way up to .338 removing the bottleneck completely?

Thangs,
Bean

6 x 45 is 223 necked up 6mm/.243. Ballistics numbers on it look good.

Though it's not a traditional AR caliber, some silhouette shooters use 7mm TCU, which is 223 necked up to 7mm/.284. I don't know if it would fit an AR magazine or not. If it did and could get a custom barrel made for it, I guess it'd work.

I have an AR pistol chambered in 7mm TCU and I have loaded bullets as heavy as 140 to magazine length. The magazine for the 7mm TCU needs to be milled out to allow for the wider neck,

SpacemanSpiff [Member]

5/19/2010 2:01:50 PM EDT

Originally Posted By Scalce:

Originally Posted By LLCoolBeans:Good enough. So long as I don't have to cut the chamber or calculate the size of the gas hole on myself, I'd be willing to purchase the entire upper. It's just more spare parts. Of course I'd rather just buy the barrel, but I suppose they hold the cards.

Great idea, just trim till the shoulder is gone and stuff a .338. Sweet.

Any ballistic data around?

It's so new that there is very little info.

Pretty much what is on their site and on Quarterbore.

225 gr.-300gr. will be subsonic and we are hoping to push the 160 gr. to about 2000 fps.

It has been done multiple times in the past as the 338 Atchisson, the the 338 Whisper, and some folks just call it the 338 Straight.

I have built an AR barrel in 338 Straight. I used a 338 neck reamer to do the neck/throat, and then added the taper to the chamber with a 300/221 reamer.

Dies are easy, just body size with a 223 die and neck size with a 338 neck sizing die.

I will be surprised if you get the 300 gr load to work in an AR-15, loaded to mag length, there is almost no room for powder with that projectile.

I am going to try to get mine to run with cast bullets.

SpacemanSpiff [Member]

5/19/2010 2:05:30 PM EDT

Originally Posted By LLCoolBeans:Good enough. So long as I don't have to cut the chamber or calculate the size of the gas hole on myself, I'd be willing to purchase the entire upper. It's just more spare parts. Of course I'd rather just buy the barrel, but I suppose they hold the cards.

Great idea, just trim till the shoulder is gone and stuff a .338. Sweet.

Kurt (7.62x40) has also done .25x40 and 6.8x40 variants based on the 556.

I have a variant of his 6.8 . . . 6.8x41.

85gr Barnes TSX = 3000fps

90gr Speer TNT =2900fps

from a 16" bbl.

dryflash3 [Team Member]

6/13/2010 6:45:11 PM EDT

Great thread LLCoolBeans, lots of good responces.

The 338 Straight sounds interesting.

DoubleARon [Team Member]

6/13/2010 6:48:32 PM EDT

Originally Posted By Scalce:

Originally Posted By LLCoolBeans:

338 Thumper?

The name doesn't ring a bell, but that appears to be a 5.56 case necked up to .338. Cool. I wrote BWE, let's see what they have to say.

From BWE Firearms:

We are just getting the info on the 338 THUMPER put together. As I get more information I will post it here. The 338 uses a 223 case cut back to the start of the shoulder and you stick a 338 bullet in it. It uses standard 223 mags and bolts. We will be carrying dies for the 338. We will be selling uppers and not full guns. We are not sure at this point if we will sell just barrels or not.

What makes this cartridge any different, or more special than the .338 Spectre, other than the smaller case capacity and harder case forming?

AeroE [Moderator]

6/13/2010 7:01:17 PM EDT

I didn't see .20 Practical listed; .223 Rem necked down to .20 caliber with no changes to the shoulder.